In recent years, in color filters for color separation used in image sensors, which are solid-state imaging devices, reduction in thickness and micronization for high resolution are in progress. Together with the progress of reduction in thickness of color filter layers which are formed using coloring agents of, for example, red, green, blue, cyan, magenta, or yellow, and micronization of pixels, reduction in thickness of silicon wafers and wiring substrates on which these color filter layers are formed is also in progress.
Accompanying the reduction in thickness of a silicon wafer, there has been a problem in that noise is caused in an image due to light from the backside. In order to suppress the light from the backside, application of light-shielding properties at the backside of the color filter, on a solder resist, and/or on a substrate by using a light-shielding black resist or the like has been studied.
Particularly, taking resolution and the like into consideration, light-shielding properties are required with respect to the wavelengths from the ultraviolet region to the infrared region. In order to realize such light-shielding properties, coloring agents of red, green, blue, cyan, magenta, yellow, or the like are used in combination, or a black dye or pigment is used to realize the light-shielding properties.
For the formation of colored layers of a color filter, a colored polymerizable composition is used (photo-lithographic method). However, since the coloring agents have light-shielding properties in any cases of using coloring agents in combination, exposure light in the exposure process cannot reach the depth (a lower layer portion) of the colored layers for forming a color filter, and as a result, curing in the vicinity of the surface of a substrate such as a silicon wafer may be insufficient. Particularly, in the case of using a black pigment such as carbon black for the purpose of maintaining light-shielding properties with respect to a region including the infrared region, transmittance of the exposure light for photo-curing in the exposure process (mainly, ultraviolet rays or a visible light) is low, and only the surface of the colored layer is cured. Therefore, there is a problem in that developability at the outermost surface of the colored layer and developability in the vicinity of the substrate in the colored layer become different, and a pattern shape of the obtained colored layer may be deteriorated.
Further, in the case of forming an image by light exposure through a mask in the exposure process, there is a problem in that the image may become wide with respect to the mask size, due to diffraction at the mask or amplification of polymerization.
Furthermore, there is another problem in that, when exposure is carried out using an exposure apparatus with high illuminance, sensitivity is increased due to reciprocity law failure, and amplification of polymerization becomes great, and as a result, the image may become too wide with respect to the mask size. Particularly, in a polymerization system in which absorbance is high at the exposure wavelength, this problem is remarkable. In a case in which exposure is carried out using g-line, h-line, i-line, or the like, when a polymerizable composition colored to be black, blue, green, or red is used, this problem is remarkable. In particular, when a polymerizable composition colored to be black or blue is used, sensitivity at the surface of the colored layer is extremely high, and there are cases in which the sensitivity is required to be greatly adjusted according to the exposure method.
The above problem is particularly remarkable when a photosensitive material having high absorbance at the exposure wavelength is used and sufficient exposure is carried out in order to ensure sufficient adhesion.
Colored layers of a color filter are usually formed through coating a colored polymerizable composition on a support such as a glass substrate or the like. A method of adding a fluoro surfactant to a polymerizable composition in order to improve the coated surface state is known (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2005-173325). However, although conventionally known fluoro surfactants or the like have an effect of flattening the colored layer surface and improving the coated surface state of the colored layer, the conventionally known fluoro surfactants or the like cannot control the sensitivity of the colored layer.
Further, a method of adding a polymerization inhibitor in order to suppress a dark reaction during storage of a polymerizable composition and to improve storability of the polymerizable composition is known (see, for example, JP-A No. 2007-34119). However, although this technology can improve storability of a polymerizable composition or suppress the curability of the whole of a polymerizable composition layer, this technology cannot be used to suppress only the curability of a surface portion of a polymerizable composition layer and to improve pattern formability.